Superconductivity in a Mixed-valent System:CeRu3Si2

Low-temperature properties characterize the hexagonal compound ${\mathrm{CeRu}}_3$ ${\mathrm{Si}}_2$ as a mixed-valent system intermediate between weakly mixed-valent systems like ${\mathrm{CeSn}}_3$ or ${\mathrm{CePd}}_3$ and strongly mixed-valent systems like ${\mathrm{CeRu}}_2$. The dimensionless ratio of the Pauli susceptibility (${\chi }_0\simeq 9.4\times {10}^{-4\mathrm{}}$ emu/mole) and the linear specific-heat coefficient ($\gamma \simeq 39$ mJ/mole ${\mathrm{K}}^2$) is about 0.8. ${\mathrm{CeRu}}_3$ ${\mathrm{Si}}_2$ exhibits type-II superconductivity below $T_c\simeq 1$ K, which is much lower than $T_c\simeq 7$ K of the La homolog.